The present invention relates to a method of forming a tubular wrapping about a product.
More specifically, the present invention relates to a method of forming a tubular wrapping about a substantially rectangular-prism-shaped product, the method being of the type comprising a first folding step in which a sheet of packing material is folded into a U about the product so that an end portion of the sheet projects crosswise to a longitudinal axis of the product and beyond the product itself; and a second folding step in which said end portion is folded further about the product to define said tubular wrapping.
The present invention may be used to advantage in the tobacco industry for forming tobacco products into packets or packs, and in particular for forming products defined by groups of packets of cigarettes into cartons, to which the following description refers purely by way of example.
In the tobacco industry, cartoning machines are used, on which a folding unit is supplied with a succession of groups of packets of cigarettes and relative sheets of packing materialxe2x80x94which may be paper or transparent material such as polypropylenexe2x80x94and performs the two folding steps described above to form, about each group of packets, a tubular wrapping coaxial with the longitudinal axis of the group.
U.S. Pat. No. 5,305,580 discloses a machine and a method for forming tubular wrapping about a rectangular-prism-shaped product, in particular a packet of cigarettes. According to such a method a sheet of packing material is folded about the product so as to define the tubular wrapping by means of a rotation of the product around its longitudinal axis.
Experience has shown that, whereas, given the way it is normally carried out, the first folding step normally results in the sheet of packing material adhering perfectly to the group of packets of cigarettes, the same does not always apply to the second step with regard to the projecting end portion of the sheet.
It is an object of the present invention to provide a packing method designed to eliminate the aforementioned drawback, and which, at the same time, provides for fast, precise wrapping and reduced maintenance. A further object of the present invention is to provide a method which is cheap and easy to implement.
According to the present invention, there is provided a method of forming a tubular wrapping about a rectangular-prism-shaped product, the method comprising a first folding step in which a sheet of packing material is folded into a U about the product so that an end portion of the sheet of packing material projects crosswise to a longitudinal axis of the product and beyond the product itself; and a second folding step in which said end portion is folded further about the product to define said tubular wrapping; and being characterized in that said end portion is subjected, in the course of said second folding step, to traction in a direction crosswise to said longitudinal axis; said first folding step being performed by placing said sheet of packing material in front of, and so as to close, an inlet of a U-shaped pocket for said product; and inserting the product and said sheet of packing material inside said pocket by moving said product against said sheet of packing material and through said inlet.
The present invention also relates to a unit for forming a tubular wrapping.
According to the present invention, there is provided a unit for forming a tubular wrapping about a rectangular-prism-shaped product having a longitudinal axis, the unit comprising first folding means for folding a sheet of packing material into a U about said product so that an end portion of the sheet of packing material projects crosswise to said longitudinal axis and beyond said product; and second folding means for folding said end portion about said product to define said tubular wrapping; and being characterized by also comprising braking means associated with said second folding means and for subjecting said end portion to traction in a direction crosswise to said longitudinal axis.